Rust Coherence Checking for Trait Implementations

This challenge focuses on implementing Rust's coherence rules for trait implementations. Understanding and enforcing these rules is crucial for writing safe and predictable Rust code, preventing ambiguity when multiple trait implementations could apply to a type.

Problem Description

Your task is to build a simplified model of Rust's coherence checking system. You will need to parse and analyze trait implementation declarations and determine if they are coherent according to a subset of Rust's actual coherence rules.

What needs to be achieved:

You need to process a collection of trait implementations and identify any that violate the coherence rules.

Key requirements:

1. Parse Input: You will receive a structured representation of trait implementations.
2. Apply Coherence Rules: Implement the following simplified coherence rules:
   • Rule 1: Orphan Rule: A trait implementation is only allowed if at least one of the following is true:
     • The trait is local to the crate (not imported from another crate).
     • The type being implemented for is local to the crate.
   • Rule 2: Uniqueness Rule: For any given trait and type pair, there can be at most one implementation. This includes implementations defined directly in the current crate and those imported from other crates (though for this challenge, we'll assume we only deal with implementations within a single conceptual "crate" for simplicity in parsing).
3. Report Violations: Identify and report all implementations that violate these rules.

Expected behavior:

Given a list of trait implementations, your program should output a list of the conflicting or invalid implementations.

Important edge cases to consider:

• Multiple implementations for the same trait and type.
• Implementations for primitive types or types from the standard library.
• Implementations for types defined within the same "crate" versus external types.
• Handling of generic types in trait and type positions. (For this simplified challenge, we will primarily focus on concrete types or simple generic types where the type parameter is also a concrete type or a simple generic).

Examples

Example 1:

Input:
[
    {
        "trait_name": "Display",
        "type_name": "String",
        "is_trait_local": false,
        "is_type_local": true
    },
    {
        "trait_name": "Display",
        "type_name": "i32",
        "is_trait_local": false,
        "is_type_local": false
    },
    {
        "trait_name": "Debug",
        "type_name": "i32",
        "is_trait_local": true,
        "is_type_local": false
    }
]
Output:
[
    {
        "trait_name": "Display",
        "type_name": "i32",
        "is_trait_local": false,
        "is_type_local": false
    }
]
Explanation: The implementation for `Display` on `i32` violates the Orphan Rule because neither `Display` nor `i32` are local.

Example 2:

Input:
[
    {
        "trait_name": "Serialize",
        "type_name": "MyStruct",
        "is_trait_local": true,
        "is_type_local": true
    },
    {
        "trait_name": "Serialize",
        "type_name": "MyStruct",
        "is_trait_local": true,
        "is_type_local": true
    },
    {
        "trait_name": "Debug",
        "type_name": "MyStruct",
        "is_trait_local": false,
        "is_type_local": true
    }
]
Output:
[
    {
        "trait_name": "Serialize",
        "type_name": "MyStruct",
        "is_trait_local": true,
        "is_type_local": true
    },
    {
        "trait_name": "Serialize",
        "type_name": "MyStruct",
        "is_trait_local": true,
        "is_type_local": true
    }
]
Explanation: The `Serialize` trait has two implementations for `MyStruct`, violating the Uniqueness Rule. Both are reported.

Example 3: (Edge Case - Generic Type)

Input:
[
    {
        "trait_name": "Clone",
        "type_name": "Vec<T>", // Represents a generic type
        "is_trait_local": false,
        "is_type_local": true // Assume Vec itself is local to the crate for this example
    },
    {
        "trait_name": "Clone",
        "type_name": "MyWrapper<T>", // Represents a generic type
        "is_trait_local": true,
        "is_type_local": false // Assume MyWrapper is defined elsewhere for this example
    },
    {
        "trait_name": "Clone",
        "type_name": "MyWrapper<i32>", // Concrete type derived from generic
        "is_trait_local": true,
        "is_type_local": false
    }
]
Output:
[
    {
        "trait_name": "Clone",
        "type_name": "MyWrapper<T>",
        "is_trait_local": true,
        "is_type_local": false
    },
    {
        "trait_name": "Clone",
        "type_name": "MyWrapper<i32>",
        "is_trait_local": true,
        "is_type_local": false
    }
]
Explanation:
- `Clone` on `Vec<T>` is valid because `Vec` is local.
- `Clone` on `MyWrapper<T>` violates the Orphan Rule because `Clone` is not local and `MyWrapper` is not local.
- `Clone` on `MyWrapper<i32>` also violates the Orphan Rule because `Clone` is not local and `MyWrapper` is not local. (Note: In real Rust, implementing for `MyWrapper<i32>` would also require `MyWrapper<T>` to be local or `Clone` to be local if `MyWrapper` is not. This example simplifies it by focusing on the `MyWrapper` itself not being local).

Constraints

• The input will be a JSON-like structure (represented as a Vec<HashMap<String, Value>> in Rust, or similar) containing objects with keys: "trait_name", "type_name", "is_trait_local", "is_type_local".
• trait_name and type_name will be strings.
• is_trait_local and is_type_local will be boolean values.
• The number of implementations will be between 1 and 100.
• Trait and type names will adhere to Rust naming conventions (alphanumeric, starting with a letter).
• Focus on correctness over extreme performance optimization.

Notes

• The input structure is simplified. In a real compiler, type resolution and import tracking are complex. For this challenge, rely on the provided is_trait_local and is_type_local flags to determine locality.
• When checking for duplicate implementations (Rule 2), consider an implementation to be a duplicate if its trait_name and type_name are identical.
• The generic type example is a simplification. Real Rust coherence for generics is much more involved. For this challenge, treat Vec<T> and MyWrapper<T> as distinct "types" for the purpose of uniqueness, but the Orphan Rule check should consider the base type's locality if it's generic. If a generic type like MyWrapper<T> is not local, then any concrete instantiation like MyWrapper<i32> will also be considered non-local for the purpose of the Orphan Rule, unless the trait itself is local.
• Your solution should return a Vec of the input structures that were found to be incoherent. If multiple identical violations exist (like in Example 2), all of them should be returned.